Processes for encapsulated toners

Abstract

A process for the preparation of encapsulated toner which comprises (1) mixing a blend of a core monomer or monomers, free radical chemical initiator, pigment, and an oil soluble shell monomer to form an organic phase; (2) dispersing the resulting organic phase in the absence of surfactant or stabilizer in an aqueous solution comprised of a water-soluble shell monomer whereby interfacial shell polymerization is initiated; (3) stirring the resulting suspension to allow completion of interfacial shell polymerization; (4) initiating free radical core polymerization by increasing the temperature of the suspension from ambient to about 75° to about 90° C.; (5) completing core polymerization by maintaining the aforementioned temperature in step (4) for an effective period of time; (6) cooling; (7) filtering; and (8) drying.

What is claimed is: 
     
       1. A process for the preparation of encapsulated toners which consists essentially of (1) mixing a blend of a core monomer or monomers, free radical chemical initiator, pigment, and an oil soluble shell monomer to form an organic phase; (2) dispersing the resulting organic phase in the absence of surfactant or stabilizer in an aqueous solution comprised of a water-soluble shell monomer whereby interfacial shell polymerization is initiated; (3) stirring the resulting suspension to allow completion of interfacial shell polymerization; (4) initiating free radical core polymerization by increasing the temperature of the suspension from ambient to about 75 to about 90° C.; (5) completing core polymerization by maintaining the aforementioned temperature in step (4) for an effective period of time; (6) cooling; (7) filtering; and (8) drying. 
     
     
       2. A surfactant free process for the preparation of encapsulated toners which consists essentially of (1) mixing a blend of a core monomer, free radical chemical initiator, pigment, and an oil soluble shell monomer to form an organic phase; (2) dispersing the resulting organic phase in the absence of surfactant or stabilizer in an aqueous solution comprised of a water-soluble shell monomer whereby interfacial shell polymerization is initiated; (3) stirring the resulting suspension to allow completion of interfacial shell polymerization; (4) initiating free radical core polymerization by increasing the temperature of the suspension to about 75 to about 90° C.; (5) completing core polymerization by maintaining the aforementioned temperature in step (4) for an effective period of time; (6) cooling; (7); filtering; and (8) drying. 
     
     
       3. A surfactant free process for the preparation of encapsulated toners which consists essentially of (1) mixing a blend of a core monomer or monomers, free radical chemical initiator, magnetite, and an oil soluble shell monomer to form an organic phase; (2) dispersing the resulting organic phase in the absence of surfactant or stabilizer in an aqueous solution comprised of a water-soluble shell monomer whereby interfacial shell polymerization is initiated; (3) stirring the resulting suspension to allow completion of interfacial shell polymerization; (4) initiating free radical core polymerization by increasing the temperature of the suspension to about 75° to about 90° C.; (5) completing core polymerization by maintaining the aforementioned temperature in step (4) for an effective period of time; (6) cooling; (7) filtering; and (8) drying. 
     
     
       4. A process in accordance with claim 1 wherein the surface of encapsulated toner compositions produced is free from residual surfactant or stabilizer. 
     
     
       5. A process in accordance with claim 1 wherein the aqueous phase is comprised of water and a water soluble shell formation monomer. 
     
     
       6. A process in accordance with claim 1 wherein the organic phase is dispersed in the aqueous phase in the absence of surfactant or stabilizer to produce particles with a mean particle size of about 5 to about 30 microns using a high shear rotor-stator homogenizer. 
     
     
       7. A process in accordance with claim 1 wherein washing of the toner product is avoided. 
     
     
       8. A process in accordance with claim 1 wherein the interfacial polycondensation of the shell monomers is accomplished at a temperature of from about 20° to about 40° C., and the free radical polymerization of the core monomer is accomplished by heating to a temperature between about 75° to about 95° C. 
     
     
       9. A process in accordance with claim 1 wherein the organic phase is comprised of a core monomer or monomers, an initiator, an oil soluble shell monomer such as an isocyanate and a pigment; and the aqueous phase is comprised of a water soluble monomer. 
     
     
       10. A process in accordance with claim 1 wherein the toner composition comprises from about 10 to about 70 percent by weight of core monomer(s), from about 5 to about 30 percent by weight of shell monomer(s) and from about 10 to about 75 percent by weight of pigment, and the resulting toner has mean particle size of from about 5 to about 30 microns, a bulk density of 0.6 to 1.0 gram/cm 3  and a resistivity of from about 1×10 3  to about 1×10 8  ohm-cm, preferably from about 5×10 4  to about 1×10 7  ohm-cm. 
     
     
       11. A process in accordance with claim 1 wherein the core monomer is an acrylate, a methacrylate, or styrene. 
     
     
       12. A process in accordance with claim 1 wherein the pigment is cyan, yellow, magenta, red, green, blue, brown, or mixtures thereof. 
     
     
       13. A process in accordance with claim 1 wherein the pigment is magnetite. 
     
     
       14. A process in accordance with claim 13 wherein the magnetite is Mapico Black. 
     
     
       15. A process in accordance with claim 1 wherein the pigment is carbon black. 
     
     
       16. A process in accordance with claim 1 wherein the shell is prepared by interfacial polymerization. 
     
     
       17. A process in accordance with claim 1 wherein the shell is a polyurea, a polyamide, a polyurethane, a polyester, or mixtures thereof. 
     
     
       18. A process in accordance with claim 2 wherein the toner contains surface additives. 
     
     
       19. A process in accordance with claim 18 wherein the surface additives are comprised of conductive components, release additives, or mixtures thereof. 
     
     
       20. A process in accordance with claim 19 wherein the conductive additives are colloidal graphite, carbon black, or mixtures thereof. 
     
     
       21. A process in accordance with claim 19 wherein the release additive is zinc stearate. 
     
     
       22. A process in accordance with claim 1 wherein the pigment is a magnetite which is acicular and is present in an amount of from about 15 to about 75 percent by weight. 
     
     
       23. A process in accordance with claim 2 wherein the magnetite is cubic and is present in an amount of from about 40 to about 75 percent by weight. 
     
     
       24. A process in accordance with claim 1 wherein the mean particle diameter thereof is from about 5 to about 30 microns. 
     
     
       25. A process in accordance with claim 1 wherein the mean particle diameter thereof is from about 16 to about 28 microns. 
     
     
       26. A process in accordance with claim 1 wherein the mean particle diameter thereof is from about 18 to about 25 microns. 
     
     
       27. A process in accordance with claim 2 wherein the mean particle diameter thereof is from about 16 to about 28 microns. 
     
     
       28. A process in accordance with claim 3 wherein the mean particle diameter thereof is from about 16 to about 28 microns. 
     
     
       29. A process in accordance with claim 4 wherein the mean particle diameter thereof is from about 16 to about 28 microns. 
     
     
       30. A process in accordance with claim 9 wherein the organic phase core monomer is an alkyl acrylate, an alkyl methacrylate, styrene or styrene derivatives; the initiator is 2,2'-azodimethylvaleronitrile, or 2,2'-azoisobutyronitrile; the oil soluble shell monomer is an isocyanate; and the aqueous phase is comprised of a water-soluble amine monomer and deionized water. 
     
     
       31. A process for the preparation of encapsulated toners which consists essentially of (1) mixing a blend of a core monomer or monomers, free radical initiator, pigment, and an oil soluble shell monomer; (2) dispersing the resulting mixture in the absence of surfactant or stabilizer in an aqueous solution comprised of a water-soluble shell monomer whereby interfacial shell polymerization is initiated; (3) initiating free radical core polymerization; and (4) completing core polymerization. 
     
     
       32. A process in accordance with claim 31 wherein subsequent to completing core polymerization, the resulting product is cooled, filtered, and dried. 
     
     
       33. A surfactant free process for the preparation of encapsulated toners which consists essentially of (1) mixing a blend of a core monomer or monomers, free radical chemical initiator, pigment, and an oil soluble shell monomer; (2) dispersing the resulting mixture in the absence of surfactant or stabilizer in an aqueous solution comprised of a water-soluble shell monomer whereby interfacial shell polymerization is initiated; (3) initiating free radical core polymerization by increasing the temperature of the suspension to about 75° to about 90° C.; and (4) completing core polymerization by maintaining the aforementioned temperature in step (3) for an effective period of time. 
     
     
       34. A process in accordance with claim 33 wherein subsequent to completing core polymerization, the resulting product is cooled, filtered, and dried. 
     
     
       35. A process in accordance with claim 2 wherein the interfacial polycondensation of the shell monomers is accomplished at a temperature of from between about 20° to about 40° C., and the free radical polymerization of the core monomer is accomplished by heating to a temperature between about 75° to about 95° C. 
     
     
       36. A process in accordance with claim 3 wherein the interfacial polycondensation of the shell monomers is accomplished at a temperature of from between about 20° to about 40° C., and the free radical polymerization of the core monomer is accomplished by heating to a temperature between about 75° to about 95° C.